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Operating Segments (Narrative) (Detail) - USD ($) $ in Millions | 9 Months Ended
--- | ---
Sep. 30, 2018 | Sep. 30, 2017
Virginia Regulation | Virginia Electric and Power Company |  |
Segment Reporting Information [Line Items] |  |
Charge associated with legislation enacted | $ 215 |
Charge associated with legislation enacted, after tax | 160 |
Operating Segments |  |
Segment Reporting Information [Line Items] |  |
After- tax net expenses | (188) | $ (1)
Operating Segments | Virginia Electric and Power Company |  |
Segment Reporting Information [Line Items] |  |
After- tax net expenses | (226) |
Operating Segments | Dominion Energy Gas Holdings, LLC |  |
Segment Reporting Information [Line Items] |  |
After- tax net expenses | (99) |
Disallowance charge | 124 |
Disallowance charge, after tax | 88 |
Write off of regulatory asset |  | 15
Write off of regulatory asset, after tax |  | 9
Operating Segments | Virginia Regulation |  |
Segment Reporting Information [Line Items] |  |
Charge associated with legislation enacted | 215 |
Charge associated with legislation enacted, after tax | 160 |
Operating Segments | Virginia Regulation | Virginia Electric and Power Company |  |
Segment Reporting Information [Line Items] |  |
Charge associated with legislation enacted | 215 |
Charge associated with legislation enacted, after tax | 160 |
Corporate and Other | Operating Segments |  |
Segment Reporting Information [Line Items] |  |
After- tax net expenses | (253) | (17)
Corporate and Other | Operating Segments | Virginia Electric and Power Company |  |
Segment Reporting Information [Line Items] |  |
After- tax net expenses | (229) | (7)
Corporate and Other | Operating Segments | Dominion Energy Gas Holdings, LLC |  |
Segment Reporting Information [Line Items] |  |
After- tax net expenses | (100) | (9)
Power Generation | Operating Segments | Virginia Regulation |  |
Segment Reporting Information [Line Items] |  |
Charge associated with legislation enacted, after tax | 109 |
Power Generation | Operating Segments | Virginia Regulation | Virginia Electric and Power Company |  |
Segment Reporting Information [Line Items] |  |
Charge associated with legislation enacted, after tax | 109 |
Power Generation | Operating Segments | Nuclear Decommissioning Trust Funds |  |
Segment Reporting Information [Line Items] |  |
Net investment earnings on nuclear decommissioning trust funds | 156 |
Net investment earnings on nuclear decommissioning trust funds, after tax | 121 |
Power Generation | Operating Segments | Virginia Legislation | Virginia Electric and Power Company |  |
Segment Reporting Information [Line Items] |  |
Asset retirement obligations | 81 |
Asset retirement obligations, after tax | 60 |
Power Generation | Operating Segments | Ash Ponds and Landfills Certain Utility Generation Facility | Virginia Legislation |  |
Segment Reporting Information [Line Items] |  |
Asset retirement obligations | 81 |
Asset retirement obligations, after tax | 60 |
Power Delivery | Operating Segments | Virginia Electric and Power Company |  |
Segment Reporting Information [Line Items] |  |
Customer settlement |  | 16
Customer settlement, after tax |  | $ 10
Power Delivery | Operating Segments | Virginia Regulation |  |
Segment Reporting Information [Line Items] |  |
Charge associated with legislation enacted, after tax | 51 |
Power Delivery | Operating Segments | Virginia Regulation | Virginia Electric and Power Company |  |
Segment Reporting Information [Line Items] |  |
Charge associated with legislation enacted, after tax | 51 |
Gas Infrastructure | Operating Segments | Federal Energy Regulatory Commission |  |
Segment Reporting Information [Line Items] |  |
Disallowance charge | 124 |
Disallowance charge, after tax | $ 88 |

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